SiC-bonded organomodified siloxanes, especially polyether siloxanes, are an industrially important substance class given their widely adjustable surfactant properties. The established route to producing these substances is the platinum metal-catalyzed addition of siloxanes and silanes bearing SiH groups onto olefinically functionalized compounds, for example onto allyl polyethers.
The use of platinum catalysts for the addition of silanes or siloxanes comprising SiH groups onto compounds comprising one or more olefinic double bonds is known (hydrosilylation) and is described, for example, in “Chemie and Technologie der Silicone”, Verlag Chemie, 1960, page 43, and in the patent literature, for example in DE-A-26 46 726, EP-A-0 075 703 and U.S. Pat. No. 3,775,452. In current industrial practice, predominantly hexachloroplatinic acid and cis-diammineplatinum(ll) chloride have become established.
Platinum catalysts often employed in the more recent past are Karstedt-type catalysts (see, for example, U.S. Pat. No. 3,814,730). These platinum catalysts are prone to deactivation and shut-down phenomena when employed in the production of organomodified siloxanes, in particular allyl polyether siloxanes, and the addition reaction thus often requires postcatalysis and/or even drastic increases in temperature.
WO-A-98/00463 describes defined solid compounds having high decomposition temperatures (144.3° C. and 138.4° C.) which by addition of selected electron-poor olefins to a Karstedt catalyst are said to provide an active and simultaneously stable catalyst system for homogeneous hydrosilylation. The enhanced activity is attributed to the introduction of strongly π-acidic ligands, such as, in particular, methylnaphthoquinone and tetraethyltetracarboxylatoethylene. The reported examples comprise adding triethylsilane onto vinyltrimethylsilane, a 100% excess of the olefin component being employed. Despite the large excess and taking into account that the vinyl group, in contrast to the allyl group, is not isomerization-active, at 50° C., this catalysis shuts down due to deactivation after 2 hours to achieve an SiH conversion of only 68%. At 73° C., this catalyst system decomposes immediately giving an SiH conversion of only 18% (P Steffanut et al., Chem. Eur. J. 1998, 4, No. 10, page 2014).
EP 1 520 870 describes a catalyst which overcomes several of the cited problems. The catalyst is produced by admixing platinum(0) complex catalyst solutions, in particular those based on commercially available Karstedt complexes, with effective amounts of activating C2-6 olefins before adding these to the hydrosilylation matrix and then carrying out the hydrosilylation at moderate temperatures, preferably at between about 20° C. and about 150° C.
Unpublished application DE 102014213507.9 describes that obtaining storage-stable preparations, particularly when using di-μ-chlorobis[chloro(cyclohexene)platinum(H)] (Pt 92), requires contacting the platinum compound with at least one compound comprising at least two oxygen atoms and also having a measurable olefinic unsaturation content.
In U.S. Pat. No. 3,516,946 Modic describes that catalysts, which may be used advantageously in the production of silicone rubbers (LSR systems), are obtainable by reacting complexes of the type [PtCl2 olefin]2 or H[PtCl2 olefin] with a cyclic alkylvinylpolysiloxane of formula [(CH2═CH)(R)SiOln to bring about thermal elimination and displacement of the olefin present in the starting complexes. The synthesis of these particular catalysts is time-consuming and, even in the case of easily displaced ethylene, necessitates a reaction performed at 60° C. over six hours. Cyclohexene, which is more difficult to substitute, is likewise estimated to require six hours, but at 70° C. From a commercial practice standpoint this method provides neither a simple, nor, a cost-effective route to novel catalyst systems.